Helical high fatigue stent-graft

ABSTRACT

An implantable prosthesis, including a generally tubular substrate and a continuous shape memory member disposed over the outer surface of the substrate. The shape memory member may include a series of zig-zag struts alternating between a first strut with a first length and a second strut with a second length different from the first length. A graft member may be positioned over the substrate and shape memory member.

PRIORITY

This application is a continuation of U.S. patent application Ser. No.14/839,802, filed Aug. 8, 2015, now U.S. Pat. No. 9,585,775, which is adivision of U.S. patent application Ser. No. 14/185,653, filed Feb. 20,2014, which is a division of U.S. patent application Ser. No.12/439,156, now U.S. Pat. No. 8,696,733, filed as a U.S. national stageapplication under 35 USC § 371 of International Application No.PCT/US2007/017985, filed Aug. 14, 2007, which claims the benefit ofpriority to U.S. Provisional Application No. 60/840,868, filed Aug. 29,2006, each of which is incorporated by reference into this applicationas if fully set forth herein.

BACKGROUND

Intraluminal prostheses used to maintain, open, or dilate blood vesselsare commonly known as stents. Stent constructions generally includelattice type cylindrical frames that define a plurality of openings.Common frameworks for stents include, for example, individual ringslinked along the length of the stent by a linking member, a continuoushelically wrapped member (that may include one or more linking members),a braid or a mesh formed into a tubular structure, and a series ofinterconnected struts. Stents may be formed by arranging one or moremembers in a pattern along a longitudinal axis to define essentially acylinder and connecting the one or more members or otherwise affixingthem in position (e.g., interconnecting with a filament). Stents mayalso be formed by cutting openings into a tube of material (e.g., shapememory).

Stents may have self-expanding and/or balloon expandable properties.Self-expanding stents are delivered to a blood vessel in a collapsedcondition and expand in vivo following the removal of a constrainingforce and/or in the presence of an elevated temperature (due to materialproperties thereof), whereas balloon expandable stents are generallycrimped onto a balloon catheter for delivery and require the outwardlydirected force of a balloon for expansion. Stents can be made of variousmetals and polymers and can include a combination of self-expanding andballoon expandable properties.

Synthetic vascular grafts are routinely used to restore the blood flowin patients suffering from vascular diseases. For example, prostheticgrafts made from expanded polytetrafluoroethylene (ePTFE) are commonlyused and have shown favorable patency rates, meaning that depending on agiven time period, the graft maintains an open lumen for the flow ofblood therethrough. Grafts formed of ePTFE include a microstructurecharacterized by spaced apart nodes connected by fibrils, the distancebetween the nodes defined as internodal distance (IND), and aregenerally extruded either as a tube or as a sheet or film that isfashioned into a tube. Grafts can also be created from fibers woven orknitted into a generally tubular shape.

It is known in the art to use stents in combination with vascular graftsto form stent-grafts. Because stent-grafts are often intraluminallydeployed in vessels of varying sizes and tortuosity, flexibility can bean important consideration. Flexibility can be imparted to a stent-graftin a variety of ways, including, for example, connection of the stent tothe one or more graft layers, configuration of the stent and/or graftlayer(s), spacing of the stent struts, rings, or members along thelength of the graft(s), etc. For example, U.S. Pat. No. 6,398,803 andU.S. Pat. No. 6,770,087 to Layne et al., which are incorporated byreference in their entirety into this application, describe a graftlayer with openings to enhance flexibility. Another importantconsideration in the design of a stent-graft is the ability of the stentto withstand stress and fatigue, caused, for example, by plasticdeformations occurring at strut junctions when the stent is subjected tocircumferential forces. Stent strength can be enhanced through materialchoice, stent configuration, arrangement and configuration of graftlayers, etc.

The following references relate to stents and stent-grafts: U.S. Pat.No. 5,282,824 to Gianturco; U.S. Pat. No. 5,507,767 to Maeda et al.;U.S. Pat. No. 5,545,211 to An et al.; U.S. Pat. No. 5,591,195 to Taheriet al.; U.S. Pat. No. 6,673,103 to Golds et al.; and U.S. Pat. No.6,984,243 to Dwyer et al., each of which is incorporated by reference inits entirety into this application.

Applicants have recognized that it would be desirable to provide astent-graft that is both flexible and able to maintain strength underhigh stress/fatigue environments, embodiments of which are describedherein along with methods of making same.

BRIEF SUMMARY

Accordingly, in one embodiment, an implantable prosthesis includes agenerally tubular substrate having inner and outer surfaces, and acontinuous shape memory member disposed over the outer surface of thesubstrate along a longitudinal axis from a first end to a second end sothat the member is exposed to ambient environment, the shape memorymember including a series of zig-zag struts alternating between a firststrut with a first length and a second strut with a second lengthdifferent from the first length, adjacent first and second strutsconnected at one end thereof to form a first angle therebetween,bisection of the angle by a line parallel to the longitudinal axisforming a second angle between the line and the first strut and a thirdangle substantially equivalent to the second angle between the line andthe second strut.

In another embodiment, a stent-graft includes a longitudinallycompressed, generally tubular substrate having a first end and a secondend along a longitudinal axis, a continuous member positioned over anouter surface of the substrate from the first end to the second end, theshape memory member including a series of zig-zag struts alternatingbetween a first strut with a first length and a second strut with asecond length different from the first length, adjacent first and secondstruts connected at one end thereof to form a first angle therebetween,bisection of the first angle by a line parallel to a longitudinal axisof the substrate forming a second angle between the line and the firststrut and a third angle substantially equivalent to the second anglebetween the line and the second strut, and a graft member attached to atleast one of the substrate and continuous member, the graft memberincluding ultra high molecular weight polyethylene fibers woven orknitted into a generally tubular shape.

In one embodiment, a method of making a stent-graft includes positioninga generally tubular substrate having a first end and a second end over amandrel, and locating a continuous shape memory member over an outersurface of the substrate from the first end to the second end so thatthe member is exposed to ambient environment, the shape memory memberincluding a series of zig-zag struts alternating between a first strutwith a first length and a second strut with a second length differentfrom the first length, adjacent first and second struts connected at oneend thereof to form a first angle therebetween, bisection of the firstangle by a line parallel to a longitudinal axis of the substrate forminga second angle between the line and the first strut and a third anglesubstantially equivalent to the second angle between the line and thesecond strut.

These and other embodiments, features and advantages will become moreapparent to those skilled in the art when taken with reference to thefollowing more detailed description of the invention in conjunction withthe accompanying drawings that are first briefly described.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a partial perspective view of one embodiment of astent-graft.

FIG. 1B is an enlarged view of one stent strut configuration of thestent-graft in FIG. 1A.

FIG. 2 is a partial perspective view of one embodiment of a stent-graftwith an outer graft member.

FIG. 3 is a partial perspective view of another embodiment of astent-graft with an outer graft member.

FIG. 4A is a partial perspective view of one embodiment of a stent-graftwith a tensioned outer graft member.

FIG. 4B is a partial perspective view of the stent-graft of FIG. 4A in abent configuration.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description should be read with reference to the drawings,in which like elements in different drawings are identically numbered.The drawings, which are not necessarily to scale, depict selectedembodiments and are not intended to limit the scope of the invention.The description illustrates by way of example, not by way of limitation,the principles of the invention. This description will clearly enableone skilled in the art to make and use the invention, and describesseveral embodiments, adaptations, variations, alternatives and uses ofthe invention, including what is presently believed to be the best modeof carrying out the invention.

As used herein, the terms “about” or “approximately” for any numericalvalues or ranges indicate a suitable dimensional tolerance that allowsthe part or collection of components to function for its intendedpurpose as described herein. Also, as used herein, the terms “patient”,“host” and “subject” refer to any human or animal subject and are notintended to limit the systems or methods to human use, although use ofthe subject invention in a human patient represents a preferredembodiment.

The stent-graft described herein may be utilized with bio-active agents.Bio-active agents can be coated onto a portion or the entirety of thestent and/or graft for controlled release of the agents once thestent-graft is implanted. The bio-active agents can include, but are notlimited to, vasodilator, anti-coagulants, such as, for example, warfarinand heparin. Other bio-active agents can also include, but are notlimited to agents such as, for example, anti-proliferative/antimitoticagents including natural products such as vinca alkaloids (i.e.vinblastine, vincristine, and vinorelbine), paclitaxel,epidipodophyllotoxins (i.e. etoposide, teniposide), antibiotics(dactinomycin (actinomycin D) daunorubicin, doxorubicin and idarubicin),anthracyclines, mitoxantrone, bleomycins, plicamycin (mithramycin) andmitomycin, enzymes (L-asparaginase which systemically metabolizesL-asparagine and deprives cells which do not have the capacity tosynthesize their own asparagine); antiplatelet agents such as G(GP)IIb/IIIa inhibitors and vitronectin receptor antagonists;anti-proliferative/antimitotic alkylating agents such as nitrogenmustards (mechlorethamine, cyclophosphamide and analogs, melphalan,chlorambucil), ethylenimines and methylmelamines (hexamethylmelamine andthiotepa), alkyl sulfonates-busulfan, nirtosoureas (carmustine (BCNU)and analogs, streptozocin), trazenes-dacarbazinine (DTIC);anti-proliferative/antimitotic antimetabolites such as folic acidanalogs (methotrexate), pyrimidine analogs (fluorouracil, floxuridine,and cytarabine), purine analogs and related inhibitors (mercaptopurine,thioguanine, pentostatin and 2-chlorodeoxyadenosine {cladribine});platinum coordination complexes (cisplatin, carboplatin), procarbazine,hydroxyurea, mitotane, aminoglutethimide; hormones (i.e. estrogen);anti-coagulants (heparin, synthetic heparin salts and other inhibitorsof thrombin); fibrinolytic agents (such as tissue plasminogen activator,streptokinase and urokinase), aspirin, dipyridamole, ticlopidine,clopidogrel, abciximab; antimigratory; antisecretory (breveldin);anti-inflammatory: such as adrenocortical steroids (cortisol, cortisone,fludrocortisone, prednisone, prednisolone, 6α-methylprednisolone,triamcinolone, betamethasone, and dexamethasone), non-steroidal agents(salicylic acid derivatives i.e. aspirin; para-aminophenol derivativesi.e. acetominophen; indole and indene acetic acids (indomethacin,sulindac, and etodalac), heteroaryl acetic acids (tolmetin, diclofenac,and ketorolac), arylpropionic acids (ibuprofen and derivatives),anthranilic acids (mefenamic acid, and meclofenamic acid), enolic acids(piroxicam, tenoxicam, phenylbutazone, and oxyphenthatrazone),nabumetone, gold compounds (auranofin, aurothioglucose, gold sodiumthiomalate); immunosuppressives: (cyclosporine, tacrolimus (FK-506),sirolimus (rapamycin), azathioprine, mycophenolate mofetil); angiogenicagents: vascular endothelial growth factor (VEGF), fibroblast growthfactor (FGF); angiotensin receptor blockers; nitric oxide donors;anti-sense oligionucleotides and combinations thereof; cell cycleinhibitors, mTOR inhibitors, and growth factor receptor signaltransduction kinase inhibitors; retenoids; cyclin/CDK inhibitors; HMGco-enzyme reductase inhibitors (statins); and protease inhibitors.

As used herein, the term “bio-resorbable” includes a suitablebio-compatible material, mixture of materials or partial components ofmaterials being degraded into other generally non-toxic materials by anagent present in biological tissue (i.e., being bio-degradable via asuitable mechanism, such as, for example, hydrolysis) or being removedby cellular activity (i.e., bioresorption, bioabsorption, orbioresorbable), by bulk or surface degradation (i.e., bioerosion suchas, for example, by utilizing a water insoluble polymer that is solublein water upon contact with biological tissue or fluid), or a combinationof one or more of the bio-degradable, bio-erodable, or bio-resorbablematerial noted above. Potential materials for the stent described hereininclude, for example, biodegradable polymers such as polylactic acid,i.e., PLA, polyglycolic acid, i.e., PGA, polydioxanone, i.e., PDS,polyhydroxybutyrate, i.e., PHB, polyhydroxyvalerate, i.e., PHV andcopolymers or a combination of PHB and PHV (available commercially asBiopol®), polycaprolactone (available as Capronor®), polyanhydrides(aliphatic polyanhydrides in the back bone or side chains or aromaticpolyanhydrides with benzene in the side chain), polyorthoesters,polyaminoacids (e.g., poly-L-lysine, polyglutamic acid),pseudo-polyaminoacids (e.g., with back bone of polyaminoacids altered),polycyanocrylates, or polyphosphazenes.

The stent may be formed of a shape memory material, including, forexample, shape memory metals, shape memory alloys, super elastic shapememory metal alloys, linear elastic shape memory alloy, shape memorypolymers, and combinations thereof. One preferred shape memory materialis Nitinol. The stent may also be formed of metals, such as, forexample, stainless steel, platinum, and Elgiloy, or certain polymers.

Potential materials for a substrate or graft member include, forexample, expanded polytetrafluoroethylene (ePTFE), polyester,polyurethane, fluoropolymers, such as perfouorelastomers and the like,polytetrafluoroethylene, silicones, urethanes, ultra high molecularweight polyethylene, aramid fibers, and combinations thereof. Onepreferred embodiment for a substrate material is ePTFE, while apreferred embodiment for a graft member material is high strengthpolymer fibers such as ultra high molecular weight polyethylene fibers(e.g., Spectra®, Dyneema Purity®, etc.) or aramid fibers (e.g.,Technora®, etc.). The substrate and/or graft member may include abioactive agent. In one embodiment, an ePTFE substrate includes a carboncomponent along a blood contacting surface thereof.

The examples discussed herein may include an ePTFE substrate. As isknown in the art, an ePTFE substrate may be manufactured in a number ofways, including, for example, extrusion of a tube (seamless), extrusionof a sheet that is subsequently formed into a tube (one or more seams),helical wrapping of ePTFE tape around a mandrel (e.g., multiple seams orpreferably a single helical seam), etc. While the preferred method usedfor forming an ePTFE substrate in the present invention is to extrude atube, it should be appreciated that other forming methods are possibleand are within the scope of the invention. The substrate and/or graftmember of the stent-graft described herein has a thickness in the rangeof approximately 10 microns and approximately 100 microns, preferably inthe range of approximately 20 microns and approximately 60 microns. Thenode-fibril microstructure of an ePTFE substrate may include variousorientations for the fibrils, but in a preferred embodiment, the fibrilsare oriented generally parallel to the longitudinal axis of thesubstrate. The average internodal distance (IND) for one preferredembodiment of a substrate and/or graft described herein is betweenapproximately 6 microns and approximately 80 microns. Also, as describedin U.S. Pat. No. 5,790,880 to Banas et al., which is incorporated byreference in its entirety in this application, the substrate and/orgraft member may be made of an ePTFE that undergoes nodal elongationduring radial expansion.

Referring now to FIG. 1A, a stent-graft 10 is illustrated, including asubstrate 12 and a stent 20. The substrate 12 in a preferred embodimentis an extruded ePTFE tube. The stent 20 in a preferred embodiment ismade of Nitinol, and more specifically, is laser cut from a Nitinol tubeinto an elongate member with a zig-zag strut configuration. In certainembodiments, the stent 20 includes two or more elongate members, but ina preferred embodiment, the stent includes a single elongate member. Inother embodiments, the stent 20 includes discrete stent members, suchas, for example, stent rings. In FIG. 1A, the elongate stent member 20is helically wound about an outer surface of the substrate 12 such thatadjacent helical windings are spaced a distance d from one another. Inone embodiment, the distance d between adjacent helical windings ofstent 20 is approximately equal along the length of the stent-graft 10.In other embodiments, the distance between adjacent helical windings maybe varied along the length of the stent-graft 10. For example, beginningat one end of the stent-graft 10, the distance between the first twohelical windings, d1, could be less than the distance d2 betweensubsequent helical windings. The distance between adjacent helicalwindings could then progressively become greater along the length of thestent-graft, could alternate between d1 and d2, etc. In embodimentsincluding two or more elongate stent members, the members could behelically wound about the substrate in different directions and/or withdifferent helical angles. In certain embodiments, the stent member 20 isplaced under tension as it is helically wound about the substrate.

Regardless of the distance between adjacent helical windings or thedirection thereof, the zig-zag struts of stent 20, in a preferredembodiment, are arranged with respect to each other and the longitudinalaxis L of the stent-graft 10 as shown in FIG. 1B. Such an arrangement isbelieved to impart to the stent-graft 10 an ability to deploy withoutsubstantially shortening. Stent member 20 includes a plurality ofzig-zag struts, including a longer first strut 22 and a shorter secondstrut 24 that alternate along the length of the stent member 20. Thefirst strut 22 and second strut 24 intersect at an apex 26 to form afirst angle Φ between the first and second struts 22, 24. The bisectionof first angle Φ by a line parallel to the longitudinal axis L of thestent-graft 10 results in two substantially equivalent second and thirdangles θ as shown in FIG. 1B. Each apex 26 forms a peak P and a trough Tand the stent member 20 includes a first set of apices 30 spaced from asecond set of apices 32 along its length.

In one embodiment, helical windings of stent member 20 are positionedalong a surface of a substrate 12 so that the peak P of apices 30 on onehelical winding is aligned with a trough T of apices 30 on an adjacenthelical winding, the adjacent windings spaced a sufficient distanceapart to prevent interference between the windings upon radialcompression of the stent-graft. For example, the stent member 20 may beattached to a substrate in an expanded configuration defining anexpanded perimeter of the stent-graft 10 and subsequently radiallycompressed for delivery to a blood vessel to a collapsed configuration,defining a collapsed perimeter of the stent-graft 10 smaller than theexpanded perimeter thereof. In another embodiment, the distance betweenadjacent helical windings is such that regardless of alignment, radialcompression of the stent-graft will not result in interlocking of thestruts.

In certain embodiments, the stent-graft will include a graft member thatis disposed over the stent member 20. FIG. 2 illustrates a stent-graft40, including an ePTFE substrate 12, an elongate stent member 20helically wound about an outer surface of the substrate 12 such thatadjacent helical windings are spaced apart along a longitudinal axis Lof the stent-graft 40 and a graft member 42 positioned about thesubstrate 12 and stent member 20. The graft member 42 includes openings44 that are circumferentially arranged in sets spaced apart fromadjacent sets, with adjacent sets of openings offset in alternatingfashion along the length of the graft member 42, as shown. It is notedthat in the embodiment shown in FIG. 2, the openings 44 are configuredand spaced apart such that the stent member 20 is substantially coveredby the material portion of the graft member 42 (e.g., the openingsinclude angled sides that correspond to the helical angle of the stentmember with respect to the longitudinal axis of the stent-graft andthese angled sides are positioned adjacent the helical windings).

The graft member in one embodiment is a continuous ePTFE member with a“lacey” graft configuration, and in another embodiment is a continuousePTFE member with a plurality of slits, such as or similar to thatdescribed in U.S. Pat. No. 6,398,803 and U.S. Pat. No. 6,770,087 toLayne et al. In an embodiment with slits in the graft member, the slitsmay be relatively small such that several slits are arranged along thegraft member. The slits may be arranged generally perpendicular to thelongitudinal axis thereof (e.g., longitudinally adjacent slits aligned,circumferentially offset, a combination thereof, etc.), generallyparallel to the longitudinal axis thereof (e.g., circumferentiallyadjacent slits aligned, longitudinally offset, a combination thereof,etc.), or some combination thereof. Alternatively, the slits may extendover a majority of the distance longitudinally or circumferentially ofthe graft member, depending on arrangement. In one embodiment the graftmember 42 is arranged such that the ePTFE material is substantiallycovering the stent member 20, while in other embodiments the graftmember 42 is arranged to reveal a small or large portion of the stentmember 20.

FIG. 3 illustrates another embodiment of a graft member positioned overan ePTFE substrate 12 having an elongate stent member 20 helically woundabout its outer surface. Stent-graft 50 includes a graft-member 52having an elongate strip of ePTFE 54 that is helically wound about thesubstrate 12 along a substantially similar path as the stent member 20to completely or partially cover the stent member 20, and one or morelongitudinal strips of ePTFE 56 disposed transverse to the helicalwindings of the stent member 20 and elongate strip of ePTFE 54. Thelongitudinal strips 56 may be disposed over the stent member 20 prior tothe winding of the elongate strip 54, subsequent to the winding of theelongate strip 54, or during the winding of the elongate strip 54 in anywoven-type pattern (e.g., the longitudinal strip 56 may be alternatelydisposed under the elongate strip 54 and over the elongate strip 54 foradjacent windings thereof). The longitudinal strips, in one embodiment,are disposed generally parallel to the longitudinal axis of thestent-graft, but in other embodiments are positioned at an angle withrespect thereto. The elongate strip 54 and/or longitudinal strips 56 maybe placed under tension during disposition about the substrate 12. Inone embodiment, stent-graft 50 will include an elongate strip of ePTFE54 helically wound about the substrate 12 without any longitudinalstrips 56. In another embodiment, a plurality of circumferential stripsare utilized along with or in place of the helically wound elongatestrip 52. Other embodiments of stent-grafts with strips and bands ofePTFE are described in U.S. Pat. No. 6,558,414 to Layne, which isincorporated by reference in its entirety in this application.

The ePTFE graft members 42, 52 in FIGS. 2 and 3, respectively, can beattached to the underlying ePTFE substrate 12 through the application ofheat and/or pressure, and/or other methods, as described, for example,in U.S. Pat. No. 6,124,523 to Banas et al., which is incorporated byreference in its entirety in this application. Adhesives and/or solventsmay also be used instead of, or in conjunction with, the aforementionedattachment methods. For example, a coating, such as urethane resin,could be disposed on sides of the stent member 20 to contact both thesubstrate and the graft member when assembled together. Thereafter, theassembly can be soaked in a solvent for bonding. Also, the stent member20 could be sutured to the substrate at various locations along thelength thereof. In one embodiment, the substrate 12 is initiallyunsintered ePTFE and is located over a mandrel for positioning of thestent member 20 and graft member, which may be sintered or partiallysintered. The assembly is then heated to sinter the substrate to thegraft member (e.g., 360 degrees C. for 10 minutes). Prior to heating,the assembly may be subject to pressures to force the separate layerstogether (e.g., by wrapping with a tape).

In certain embodiments, the stent-graft may include a plurality ofmarkers arranged along its length for visualization of the stent-graftin vivo. In one embodiment, the markers include a radiopaque material,such as barium sulfate or hydroxyapatite, to increase visibility underradio imaging (e.g., x-ray).

FIGS. 4A and 4B illustrate a stent-graft 60 including a substrate 12, astent member 62 and a graft member 70. The graft member 70 has agenerally tubular shape and is configured in a honeycomb-type pattern orlattice structure, including a plurality of cells 72 with each cell 72having a central opening 74. While the central opening 74 has a heptagonshape in the embodiment shown, other geometric shapes, includingpolygonal shapes, are possible and within the scope of the invention.The cells 72 are connected together via hinges 76, each hinge includinga point of pivot to permit rotational pivoting motion thereof. In oneembodiment, the hinges 76 are arranged in spaced apart sets of two, thefirst hinge in a given set positioned circumferentially approximately180 degrees apart from the second hinge, and adjacent sets of hinges arerotated approximately 90 degrees from one another. Thus, for example,referring to FIG. 4A, longitudinal hinges 76 a connect adjacent cells 72in a first row of cells and adjacent cells 72 in a second row of cellslocated opposite the first row of cells (spaced circumferentiallyapproximately 180 degrees therefrom), while circumferential hinges 76 b,rotated approximately 90 degrees with respect to longitudinal hinges 76a, connect each cell in the first row of cells with its circumferentialcounterpart in the second row of cells in two locations spacedapproximately 180 degrees apart (i.e., first row cells are connected tosecond row cells at approximately the same axial position along thelongitudinal axis by two circumferential hinges).

In one embodiment, the materials for the stent-graft 60 include ePTFEfor the substrate 12, shape memory material for stent 62 and a knittedor woven network of high strength polymer fibers such as ultra highmolecular weight polyethylene fibers (e.g., Spectra®, Dyneema Purity®,etc.) or aramid fibers (e.g., Technora®, etc.) for graft member 70. Inone method of assembly, the substrate 12 is positioned over a mandreland longitudinally compressed in a range of approximately 50% toapproximately 95% of its original, uncompressed length. While thesubstrate 12 is held in its compressed state, the shape memory member 62is located thereover. For example, if the shape memory stent 62 is anelongate member including zig-zag struts, such as stent member 20, thelocating step includes helical winding the shape memory member 62 aboutthe compressed substrate 12. Once the shape memory member 62 is inposition, the graft member 70 is placed over the shape memory member 62and compressed substrate 12. The graft member 70 is then placed undertension (e.g., proximal and distal ends of the graft member are pulledin opposite directions) and clamped or otherwise fixed in place over theshape memory member 62 and compressed substrate 12. In this tensionedstate, the material of the graft member 70 may cover substantially allof, or only a portion of, an outer surface of the shape memory member62. The stent-graft 60 in its assembled form is then preferablycontacted with a polymeric adhesive, such as polyurethane, to bond thegraft member 70 to the shape memory member 62 and/or the substrate 12.Optionally, the polymeric adhesive can be activated by a solvent, suchas tetrahydrofuran (THF). Other modes of attachment (e.g., resin,sutures, heat, pressure, etc.) may also be used in conjunction with thesolvent to assist in bonding.

In FIG. 4B, a portion of the stent-graft 60 made according to theaforementioned method is shown in a curved state. Due to thelongitudinal compression of the substrate 12 and flexibility of thegraft member 70, the portion of the stent-graft 60 following the longerpath of curvature Cl stretches, while the portion of the stent-graft 60following the shorter path of curvature Cs compresses, such thatstructural integrity of the stent-graft 60 is maintained. Thelongitudinal hinges 76 a and circumferential hinges 76 b togetherproduce a multiple hinge effect in graft member 70, which impartsenhanced flexibility to the graft member 70. The bending freedom of thesubstrate 12 together with the flexibility of the graft member 70 (dueat least in part to the rotational freedom of the hinges 76) is believedto impart superior kink resistance to the stent-graft 60 such that thestent-graft 60 is able to navigate tortuous bends without kinking.Moreover, the graft member 70 in this embodiment acts to prevent thestent member 62 from lengthening in vivo, thereby increasing theeffective radial strength of the stent member 62. This is believed to bedue to one or more of the characteristics of the graft member 70,including, but not limited to, the configuration of the graft member(network of cells and hinges), the material of the graft member (highstrength polymer fibers), the formation of the graft member (woven orknitted fibers), the pre-attachment tensioning of the graft memberand/or the attachment of the graft member to the substrate 12 and stentmember 62 through use of a solvent.

This invention has been described and specific examples have beenportrayed. While the invention has been described in terms of particularvariations and illustrative figures, those of ordinary skill in the artwill recognize that the invention is not limited to the variations orfigures described. In addition, where methods and steps described aboveindicate certain events occurring in certain order, those of ordinaryskill in the art will recognize that the ordering of certain steps maybe modified and that such modifications are in accordance with thevariations of the invention. Additionally, certain of the steps may beperformed concurrently in a parallel process when possible, as well asperformed sequentially as described above. Therefore, to the extentthere are variations of the invention, which are within the spirit ofthe disclosure or equivalent to the inventions found in the claims, itis the intent that this patent will cover those variations as well.Finally, all publications and patent applications cited in thisspecification are herein incorporated by reference in their entirety asif each individual publication or patent application were specificallyand individually put forth herein.

What is claimed is:
 1. A stent-graft, comprising: a longitudinallycompressed, generally tubular substrate having a first end and a secondend along a longitudinal axis; a continuous member positioned over anouter surface of the substrate from the first end to the second end, thecontinuous member including a series of zigzag struts alternatingbetween a first strut with a first length and a second strut with asecond length different from the first length, adjacent first and secondstruts connected at one end thereof to form a first angle therebetween,bisection of the first angle by a line parallel to a longitudinal axisof the substrate forming a second angle between the line and the firststrut, and a third angle equivalent to the second angle between the lineand the second strut; and a graft member attached to at least one of thesubstrate and continuous member in a tensioned state, the graft memberincluding polymer fibers woven or knitted into a generally tubularshape.
 2. The stent-graft according to claim 1, wherein the polymerfibers are selected from a group consisting essentially of polyester,polyurethanes, fluoropolymers, ultra high molecular weight polyethylene,polyamide, aramid fibers, and combinations thereof.
 3. The stent-graftaccording to claim 1, wherein the substrate comprises ePTFE.
 4. Thestent-graft according to claim 1, further comprising an adhesivedisposed between the continuous member and the graft member.
 5. Thestent-graft according to claim 1, wherein the continuous membercomprises a material selected from the group consisting essentially ofstainless steel, shape memory metals, shape memory alloys, super elasticshape memory metal alloys, metal alloys, linear elastic shape memoryalloy, shape memory polymers, polymers, bio-resorbable materials, andcombinations thereof.
 6. The stent-graft according to claim 1, whereinthe graft member includes a plurality of circumferentially arranged setsof openings, adjacent sets spaced apart along a longitudinal axis of thegraft member, the graft member arranged such that a surface of thecontinuous member is substantially covered by the graft member.
 7. Thestent-graft according to claim 1, wherein the graft member comprises anetwork of cells connected by hinges, and wherein the cells include acentral opening defining a geometric shape.
 8. The stent-graft accordingto claim 7, wherein the cells are arranged along the longitudinal axisin a first row and a second row spaced circumferentially 180 degreesfrom the first row.
 9. The stent-graft according to claim 8, whereinadjacent cells along the first row are connected by a first longitudinalhinge and adjacent cells in the second row are connected together via asecond longitudinal hinge.
 10. The stent-graft according to claim 9,wherein first row cells are connected to second row cells at the sameaxial position along the longitudinal axis by a first circumferentialhinge and a second circumferential hinge spaced 180 degrees from thefirst circumferential hinge.
 11. The stent-graft according to claim 10,wherein the circumferential hinges are rotated 90 degrees with respectto the longitudinal hinges.
 12. A stent-graft, comprising: a tubularsubstrate having a first end and a second end along a longitudinal axis,the tubular substrate having a first relaxed length and a secondcompressed length less than the first relaxed length; a continuousmember positioned over an outer surface of the substrate from the firstend to the second end at the second compressed length; and a graftmember attached to at least one of the substrate and continuous memberin a tensioned state, the graft member including polymer fibers woven orknitted into a generally tubular shape.
 13. The stent-graft according toclaim 12, wherein: the substrate comprises ePTFE, the continuous membercomprises a material selected from the group consisting essentially ofstainless steel, shape memory metals, shape memory alloys, super elasticshape memory metal alloys, metal alloys, linear elastic shape memoryalloy, shape memory polymers, polymers, bio-resorbable materials, andcombinations thereof, and the polymer fibers are selected from a groupconsisting essentially of polyester, polyurethanes, fluoropolymers,ultra high molecular weight polyethylene, polyamide, aramid fibers, andcombinations thereof.
 14. The stent-graft according to claim 12, whereinthe continuous member includes a series of zigzag struts alternatingbetween a first strut with a first length and a second strut with asecond length different from the first length, adjacent first and secondstruts connected at one end thereof to form a first angle therebetween,bisection of the first angle by a line parallel to a longitudinal axisof the substrate forming a second angle between the line and the firststrut, and a third angle equivalent to the second angle between the lineand the second strut.
 15. The stent-graft according to claim 12, whereinthe graft member includes a plurality of circumferentially arranged setsof openings, adjacent sets spaced apart along a longitudinal axis of thegraft member, the graft member arranged such that a surface of thecontinuous member is substantially covered by the graft member.
 16. Thestent-graft according to claim 12, wherein the graft member comprises anetwork of cells connected by hinges, and wherein the cells include acentral opening defining a geometric shape.
 17. The stent-graftaccording to claim 16, wherein the cells are arranged along thelongitudinal axis in a first row and a second row spacedcircumferentially 180 degrees from the first row.
 18. The stent-graftaccording to claim 17, wherein adjacent cells along the first row areconnected by a first longitudinal hinge and adjacent cells in the secondrow are connected together via a second longitudinal hinge.
 19. Thestent-graft according to claim 18, wherein first row cells are connectedto second row cells at the same axial position along the longitudinalaxis by a first circumferential hinge and a second circumferential hingespaced 180 degrees from the first circumferential hinge.
 20. Thestent-graft according to claim 19, wherein the circumferential hingesare rotated 90 degrees with respect to the longitudinal hinges.